Conflict resolution for blockchain storage structure

ABSTRACT

An example operation may include one or more of receiving a content request to add a content to a blockchain storage structure implemented on a blockchain database, temporarily storing the content of the content request in a queue implemented via the blockchain database based on when the request is received, receiving a request to flush the queue which is invoked by chaincode, and in response to the flush request, removing the content from the queue and adding the content to the blockchain storage structure.

TECHNICAL FIELD

This application generally relates to a process for tracking behavior anonymously, and more particularly, to a blockchain which manage a storage structure for tracking data without knowing or revealing an identify of the participant whose data is being tracked.

BACKGROUND

A centralized database stores and maintains data in a single database (e.g., a database server) at one location. This location is often a central computer, for example, a desktop central processing unit (CPU), a server CPU, or a mainframe computer. Information stored on a centralized database is typically accessible from multiple different points. Multiple users or client workstations can work simultaneously on the centralized database, for example, based on a client/server configuration. A centralized database is easy to manage, maintain, and control, especially for purposes of security because of its single location. Within a centralized database, data redundancy is minimized as a single storing place of all data also implies that a given set of data only has one primary record.

However, a centralized database suffers from significant drawbacks. For example, a centralized database has a single point of failure. In particular, if there are no fault-tolerance considerations and a hardware failure occurs (for example a hardware, firmware, and/or a software failure), all data within the database is lost and work of all users is interrupted. In addition, centralized databases are highly dependent on network connectivity. As a result, the slower the connection, the amount of time needed for each database access is increased. Another drawback is the occurrence of bottlenecks when a centralized database experiences high traffic due to a single location. Furthermore, a centralized database provides limited access to data because only one copy of the data is maintained by the database. As a result, multiple devices cannot access the same piece of data at the same time without creating significant problems or risk overwriting stored data. Furthermore, because a database storage system has minimal to no data redundancy, data that is unexpectedly lost is very difficult to retrieve other than through manual operation from back-up storage.

In effort to address the deficiencies in security, immutability, and central authority, organizations have begun turning to blockchain to store data. For example, supply chain data (e.g., between different untrusting participants of the supply chain, etc.) may be recorded in a trusted manner through the use of blockchain. However, typically the information stored on the blockchain is viewable/available to all of the participants of the blockchain. As such, what is needed is a solution that can track information anonymously.

SUMMARY

One example embodiment provides a system that includes one or more of a network interface configured to receive a content request to add content to a blockchain storage structure implemented on a blockchain database, an a processor configured to one or more of temporarily store the content of the content request in a queue implemented via the blockchain database based on when the request is received, receive a request to flush the queue which is invoked by chaincode, and in response to the flush request, remove the content from the queue and add the content to the blockchain storage structure.

Another example embodiment provides a method that includes one or more receiving a content request to add a content to a blockchain storage structure implemented on a blockchain database, temporarily storing the content of the content request in a queue implemented via the blockchain database based on when the request is received, receiving a request to flush the queue which is invoked by chaincode, and in response to the flush request, removing the content from the queue and adding the content to the blockchain storage structure.

A further example embodiment provides a non-transitory computer readable medium comprising instructions, that when read by a processor, cause the processor to perform one or more of receiving a content request to add a content to a blockchain storage structure implemented on a blockchain database, temporarily storing the content of the content request in a queue implemented via the blockchain database based on when the request is received, receiving a request to flush the queue which is invoked by chaincode, and in response to the flush request, removing the content from the queue and adding the content to the blockchain storage structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a blockchain network including storing behavior data of supply chain participants, according to example embodiments.

FIG. 2A is a diagram illustrating an example blockchain architecture configuration, according to example embodiments.

FIG. 2B is a diagram illustrating a blockchain transactional flow, according to example embodiments.

FIG. 3A is a diagram illustrating a permissioned network, according to example embodiments.

FIG. 3B is a diagram illustrating another permissioned network, according to example embodiments.

FIG. 4A is a diagram illustrating a process of adding a new active leaf node to a blockchain structure, according to example embodiments.

FIG. 4B is a diagram illustrating a process of invoking a new active leaf node by a blockchain participant, according to example embodiments.

FIG. 4C is a diagram illustrating a queue which is implemented via a blockchain ledger for preventing storage conflicts, according to example embodiments.

FIG. 5A is a flow diagram illustrating a method of updating anonymous behavior on a blockchain structure, according to example embodiments.

FIG. 5B is a flow diagram illustrating a method of managing a queue via a blockchain ledger, according to example embodiments.

FIG. 6A is a diagram illustrating an example system configured to perform one or more operations described herein, according to example embodiments.

FIG. 6B is a diagram illustrating another example system configured to perform one or more operations described herein, according to example embodiments.

FIG. 6C is a diagram illustrating a further example system configured to utilize a smart contract, according to example embodiments.

FIG. 6D is a diagram illustrating yet another example system configured to utilize a blockchain, according to example embodiments.

FIG. 7A is a diagram illustrating a process for a new block being added to a distributed ledger, according to example embodiments.

FIG. 7B is a diagram illustrating contents of a new data block, according to example embodiments.

FIG. 7C is a diagram illustrating a blockchain for digital content, according to example embodiments.

FIG. 7D is a diagram illustrating a block which may represent the structure of blocks in the blockchain, according to example embodiments.

FIG. 8 is a diagram illustrating an example system that supports one or more of the example embodiments.

DETAILED DESCRIPTION

It will be readily understood that the instant components, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of at least one of a method, apparatus, non-transitory computer readable medium and system, as represented in the attached figures, is not intended to limit the scope of the application as claimed but is merely representative of selected embodiments.

The instant features, structures, or characteristics as described throughout this specification may be combined or removed in any suitable manner in one or more embodiments. For example, the usage of the phrases “example embodiments”, “some embodiments”, or other similar language, throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment. Thus, appearances of the phrases “example embodiments”, “in some embodiments”, “in other embodiments”, or other similar language, throughout this specification do not necessarily all refer to the same group of embodiments, and the described features, structures, or characteristics may be combined or removed in any suitable manner in one or more embodiments.

In addition, while the term “message” may have been used in the description of embodiments, the application may be applied to many types of networks and data. Furthermore, while certain types of connections, messages, and signaling may be depicted in exemplary embodiments, the application is not limited to a certain type of connection, message, and signaling.

Example embodiments provide methods, systems, components, non-transitory computer readable media, devices, and/or networks, which provide a system and method for privacy-preserving anomalous behavior detection and tracking.

In one embodiment the system utilizes a decentralized database (such as a blockchain) that is a distributed storage system, which includes multiple nodes that communicate with each other. The decentralized database includes an append-only immutable data structure resembling a distributed ledger capable of maintaining records between mutually untrusted parties. The untrusted parties are referred to herein as peers or peer nodes. Each peer maintains a copy of the database records and no single peer can modify the database records without a consensus being reached among the distributed peers. For example, the peers may execute a consensus protocol to validate blockchain storage transactions, group the storage transactions into blocks, and build a hash chain over the blocks. This process forms the ledger by ordering the storage transactions, as is necessary, for consistency. In various embodiments, a permissioned and/or a permissionless blockchain can be used. In a public or permission-less blockchain, anyone can participate without a specific identity. Public blockchains often involve native cryptocurrency and use consensus based on various protocols such as Proof of Work (PoW). On the other hand, a permissioned blockchain database provides secure interactions among a group of entities which share a common goal but which do not fully trust one another, such as businesses that exchange funds, goods, information, and the like.

This system can utilize a blockchain that operates arbitrary, programmable logic, tailored to a decentralized storage scheme and referred to as “smart contracts” or “chaincodes.” In some cases, specialized chaincodes may exist for management functions and parameters which are referred to as system chaincode. The application can further utilize smart contracts that are trusted distributed applications which leverage tamper-proof properties of the blockchain database and an underlying agreement between nodes, which is referred to as an endorsement or endorsement policy. Blockchain transactions associated with this application can be “endorsed” before being committed to the blockchain while transactions, which are not endorsed, are disregarded. An endorsement policy allows chaincode to specify endorsers for a transaction in the form of a set of peer nodes that are necessary for endorsement. When a client sends the transaction to the peers specified in the endorsement policy, the transaction is executed to validate the transaction. After validation, the transactions enter an ordering phase in which a consensus protocol is used to produce an ordered sequence of endorsed transactions grouped into blocks.

This system can utilize nodes that are the communication entities of the blockchain system. A “node” may perform a logical function in the sense that multiple nodes of different types can run on the same physical server. Nodes are grouped in trust domains and are associated with logical entities that control them in various ways. Nodes may include different types, such as a client or submitting-client node which submits a transaction-invocation to an endorser (e.g., peer), and broadcasts transaction-proposals to an ordering service (e.g., ordering node). Another type of node is a peer node which can receive client submitted transactions, commit the transactions and maintain a state and a copy of the ledger of blockchain transactions. Peers can also have the role of an endorser, although it is not a requirement. An ordering-service-node or orderer is a node running the communication service for all nodes, and which implements a delivery guarantee, such as a broadcast to each of the peer nodes in the system when committing transactions and modifying a world state of the blockchain, which is another name for the initial blockchain transaction which normally includes control and setup information.

This system can utilize a ledger that is a sequenced, tamper-resistant record of all state transitions of a blockchain. State transitions may result from chaincode invocations (i.e., transactions) submitted by participating parties (e.g., client nodes, ordering nodes, endorser nodes, peer nodes, etc.). Each participating party (such as a peer node) can maintain a copy of the ledger. A transaction may result in a set of asset key-value pairs being committed to the ledger as one or more operands, such as creates, updates, deletes, and the like. The ledger includes a blockchain (also referred to as a chain) which is used to store an immutable, sequenced record in blocks. The ledger also includes a state database which maintains a current state of the blockchain.

This system can utilize a chain that is a transaction log which is structured as hash-linked blocks, and each block contains a sequence of N transactions where N is equal to or greater than one. The block header includes a hash of the block's transactions, as well as a hash of the prior block's header. In this way, all transactions on the ledger may be sequenced and cryptographically linked together. Accordingly, it is not possible to tamper with the ledger data without breaking the hash links. A hash of a most recently added blockchain block represents every transaction on the chain that has come before it, making it possible to ensure that all peer nodes are in a consistent and trusted state. The chain may be stored on a peer node file system (i.e., local, attached storage, cloud, etc.), efficiently supporting the append-only nature of the blockchain workload.

The current state of the immutable ledger represents the latest values for all keys that are included in the chain transaction log. Since the current state represents the latest key values known to a channel, it is sometimes referred to as a world state. Chaincode invocations execute transactions against the current state data of the ledger. To make these chaincode interactions efficient, the latest values of the keys may be stored in a state database. The state database may be simply an indexed view into the chain's transaction log, it can therefore be regenerated from the chain at any time. The state database may automatically be recovered (or generated if needed) upon peer node startup, and before transactions are accepted.

The example embodiments provide a system that has the ability to anonymously track the behavior(and detect anomalous behavior) of an entity (e.g. a supply-chain participant, a patient, a gaming user, etc.) on blockchain, based on storing and updating some relevant statistics related to the entity's inputs (e.g. ratings to a supplier, medical records, gaming information, etc.) while preserving the privacy of the entity. According to various aspects, the system can maintain a Merkle tree for some entities (e.g., a supplier) that participate in the blockchain. Each Merkle tree may include an “active leaf” for each user (e.g., a buyer) of that entity (e.g., supplier).

The buyer's “active leaf” may store a standard cryptographic hash (e.g., sha256) value of a pre-image that includes a concatenation of a secret (known only to the Buyer) which is a random bit string, its current rating sum (encoded as a bit string), and its current number of ratings (encoded as a bit string). Therefore, an accumulation of the buyer's anonymous activity/behavior can be stored in the active leaf node based on a total number of reviews plus the summation of all the ratings provided by the buyer. Accordingly, a rating history of a buyer may be maintained anonymously, without the need to disclose an identity of the buyer.

Some benefits of the instant solutions described and depicted herein include the ability to accumulate behavioral information about a participant of the blockchain while still preserving the privacy of the participant. Although the examples described herein refer to the anonymous behavior of a buyer providing reviews/ratings to a seller in a supply chain network, the example embodiments are not limited thereto. As another example, anonymous bidding on blockchain may be tracked. In this example, the bidders are anonymous and are allowed to update their bids up to a fixed number of times. The auctioneer can detect a bidder's anomalous bid sequence using the example embodiments wherein the active leaf of a bidder stores the cryptographic hash of the number of bid updates made and the zero-knowledge proof verifies that this number is below a threshold.

As another example, the embodiments may be used for anonymous patient health monitoring. In this example, the blockchain may maintain a system to detect anomalies in the sequence of health indicator datapoints of patients. For each patient, measurements of some indicator of the patient's health may be taken periodically and sent as anonymous inputs to the system. In this example, a datapoint which is outside a predefined region (e.g., such as described by the mean and/or variance of the sequence, etc.) may be considered anomalous. This can be detected using the system described in the example embodiments wherein the active leaf of a patient stores the cryptographic hash of the number of datapoints, the current sum, and current sum of squares, which are sufficient to compute and update the mean and variance. The zero-IBM knowledge proof can be used to ensure that the new datapoint is within the region described by the current mean and variance.

FIG. 1 illustrates a blockchain network 100 including storing behavior data of supply chain participants, according to example embodiments. Referring to FIG. 1, the blockchain network 100 includes a blockchain 120 which stores supply chain data between suppliers 111 and 112 and buyers 131, 132, 133, and 134. For example, the blockchain 120 may store work orders, invoices, signed documents, digital goods, and the like. Although not shown in FIG. 1, the blockchain 120 may be implemented by a plurality of peer nodes which may include committing nodes, endorser nodes, orderer nodes, and the like. In some cases, a node may fulfill more than one node role.

According to various embodiments, the nodes that implement the blockchain 120 may each maintain smart contracts (which are executable chaincode), a ledger distributed/replicated among the nodes, and an immutable chain of blocks which are stored on the ledger. The ledger may be a key-value store (KVS) accessible to the smart contracts which are executed to programmatically maintain and update data on the ledger. The suppliers 111 and 112 and the buyers 131-134 may access the blockchain 120 via one or more trusted nodes.

According to various embodiments, behavior data of the participants of the supply chain may be stored anonymously via the blockchain 120. For example, the smart contracts implemented by the nodes of the blockchain 120 may store and manage Merkle trees (or other data structures) as key-values in the ledger which can be used to anonymously store behavior information of the buyers 131-134, in this example. The execution of a smart contracts are transactions consisting of read and write sets of the key-values accessed during the execution. These sets are included in a block of transactions appended to the chain of blocks on the blockchain 120. The ledger and the chain of blocks are identically updated on every peer in the blockchain network according to a consensus protocol.

In the examples herein, behavior such as ratings and reviews of the Suppliers 111-112 performed by the buyers 131-134 may be recorded on the Merkle trees in the key-value store of the blockchain 120. In some embodiments, the nodes may maintain a separate Merkle tree for each supplier 111 and 112 and each buyer 131, 132, 133, and 134 may have a dedicated active leaf in the respective Merkle trees. To implement the anonymous accumulation of data such as ratings/reviews over time, the nodes may rely on non-interactive zero knowledge proofs with (i) the buyer (client) generating the proof, and (ii) the smart contract (chaincode) verifying the proof against the ledger's data. The zero-knowledge proof allows a buyer to submit new review information and nullify old review information while preserving an identity of the buyer. In other words, new active leaves are added (and used) anonymously. The smart contracts may include API enhancements to efficiently achieve shared anonymous data update.

As the buyers 131-134 and suppliers 111-112 engage in supply chain activities, the buyers may continuously upload reviews regarding the suppliers 111-112 in an anonymous way ensuring that both the suppliers 111-112 are performing well, and also to ensure that buyers 131-134 are not continuously giving negative reviews.

FIG. 2A illustrates a blockchain architecture configuration 200, according to example embodiments. Referring to FIG. 2A, the blockchain architecture 200 may include certain blockchain elements, for example, a group of blockchain nodes 202. The blockchain nodes 202 may include one or more nodes 204-210 (these four nodes are depicted by example only). These nodes participate in a number of activities, such as blockchain transaction addition and validation process (consensus). One or more of the blockchain nodes 204-210 may endorse transactions based on endorsement policy and may provide an ordering service for all blockchain nodes in the architecture 200. A blockchain node may initiate a blockchain authentication and seek to write to a blockchain immutable ledger stored in blockchain layer 216, a copy of which may also be stored on the underpinning physical infrastructure 214. The blockchain configuration may include one or more applications 224 which are linked to application programming interfaces (APIs) 222 to access and execute stored program/application code 220 (e.g., chaincode, smart contracts, etc.) which can be created according to a customized configuration sought by participants and can maintain their own state, control their own assets, and receive external information. This can be deployed as a transaction and installed, via appending to the distributed ledger, on all blockchain nodes 204-210.

The blockchain base or platform 212 may include various layers of blockchain data, services (e.g., cryptographic trust services, virtual execution environment, etc.), and underpinning physical computer infrastructure that may be used to receive and store new transactions and provide access to auditors which are seeking to access data entries. The blockchain layer 216 may expose an interface that provides access to the virtual execution environment necessary to process the program code and engage the physical infrastructure 214. Cryptographic trust services 218 may be used to verify transactions such as asset exchange transactions and keep information private.

The blockchain architecture configuration of FIG. 2A may process and execute program/application code 220 via one or more interfaces exposed, and services provided, by blockchain platform 212. The code 220 may control blockchain assets. For example, the code 220 can store and transfer data, and may be executed by nodes 204-210 in the form of a smart contract and associated chaincode with conditions or other code elements subject to its execution. As a non-limiting example, smart contracts may be created to execute reminders, updates, and/or other notifications subject to the changes, updates, etc. The smart contracts can themselves be used to identify rules associated with authorization and access requirements and usage of the ledger. For example, anonymous data 226 may be processed by one or more processing entities (e.g., virtual machines) included in the blockchain layer 216. The result 228 may include new active leaf data for a Merkle tree stored on the blockchain in association with the anonymous data 226. The physical infrastructure 214 may be utilized to retrieve any of the data or information described herein.

A smart contract may be created via a high-level application and programming language, and then written to a block in the blockchain. The smart contract may include executable code which is registered, stored, and/or replicated with a blockchain (e.g., distributed network of blockchain peers). A transaction is an execution of the smart contract code which can be performed in response to conditions associated with the smart contract being satisfied. The executing of the smart contract may trigger a trusted modification(s) to a state of a digital blockchain ledger. The modification(s) to the blockchain ledger caused by the smart contract execution may be automatically replicated throughout the distributed network of blockchain peers through one or more consensus protocols.

The smart contract may write data to the blockchain in the format of key-value pairs. Furthermore, the smart contract code can read the values stored in a blockchain and use them in application operations. The smart contract code can write the output of various logic operations into the blockchain. The code may be used to create a temporary data structure in a virtual machine or other computing platform. Data written to the blockchain can be public and/or can be encrypted and maintained as private. The temporary data that is used/generated by the smart contract is held in memory by the supplied execution environment, then deleted once the data needed for the blockchain is identified.

A chaincode may include the code interpretation of a smart contract, with additional features. As described herein, the chaincode may be program code deployed on a computing network, where it is executed and validated by chain validators together during a consensus process. The chaincode receives a hash and retrieves from the blockchain a hash associated with the data template created by use of a previously stored feature extractor. If the hashes of the hash identifier and the hash created from the stored identifier template data match, then the chaincode sends an authorization key to the requested service. The chaincode may write to the blockchain data associated with the cryptographic details.

FIG. 2B illustrates an example of a blockchain transactional flow 250 between nodes of the blockchain in accordance with an example embodiment. Referring to FIG. 2B, the transaction flow may include a transaction proposal 291 sent by an application client node 260 to an endorsing peer node 281. The endorsing peer 281 may verify the client signature and execute a chaincode function to initiate the transaction. The output may include the chaincode results, a set of key/value versions that were read in the chaincode (read set), and the set of keys/values that were written in chaincode (write set). The proposal response 292 is sent back to the client 260 along with an endorsement signature, if approved. The client 260 assembles the endorsements into a transaction payload 293 and broadcasts it to an ordering service node 284. The ordering service node 284 then delivers ordered transactions as blocks to all peers 281-283 on a channel. Before committal to the blockchain, each peer 281-283 may validate the transaction. For example, the peers may check the endorsement policy to ensure that the correct allotment of the specified peers have signed the results and authenticated the signatures against the transaction payload 293.

Referring again to FIG. 2B, the client node 260 initiates the transaction 291 by constructing and sending a request to the peer node 281, which is an endorser. The client 260 may include an application leveraging a supported software development kit (SDK), which utilizes an available API to generate a transaction proposal. The proposal is a request to invoke a chaincode function so that data can be read and/or written to the ledger (i.e., write new key value pairs for the assets). The SDK may serve as a shim to package the transaction proposal into a properly architected format (e.g., protocol buffer over a remote procedure call (RPC)) and take the client's cryptographic credentials to produce a unique signature for the transaction proposal.

In response, the endorsing peer node 281 may verify (a) that the transaction proposal is well formed, (b) the transaction has not been submitted already in the past (replay-attack protection), (c) the signature is valid, and (d) that the submitter (client 260, in the example) is properly authorized to perform the proposed operation on that channel. The endorsing peer node 281 may take the transaction proposal inputs as arguments to the invoked chaincode function. The chaincode is then executed against a current state database to produce transaction results including a response value, read set, and write set. However, no updates are made to the ledger at this point. In 292, the set of values, along with the endorsing peer node's 281 signature is passed back as a proposal response 292 to the SDK of the client 260 which parses the payload for the application to consume.

In response, the application of the client 260 inspects/verifies the endorsing peers signatures and compares the proposal responses to determine if the proposal response is the same. If the chaincode only queried the ledger, the application would inspect the query response and would typically not submit the transaction to the ordering node service 284. If the client application intends to submit the transaction to the ordering node service 284 to update the ledger, the application determines if the specified endorsement policy has been fulfilled before submitting (i.e., did all peer nodes necessary for the transaction endorse the transaction). Here, the client may include only one of multiple parties to the transaction. In this case, each client may have their own endorsing node, and each endorsing node will need to endorse the transaction. The architecture is such that even if an application selects not to inspect responses or otherwise forwards an unendorsed transaction, the endorsement policy will still be enforced by peers and upheld at the commit validation phase.

After successful inspection, in step 293 the client 260 assembles endorsements into a transaction and broadcasts the transaction proposal and response within a transaction message to the ordering node 284. The transaction may contain the read/write sets, the endorsing peers signatures and a channel ID. The ordering node 284 does not need to inspect the entire content of a transaction in order to perform its operation, instead the ordering node 284 may simply receive transactions from all channels in the network, order them chronologically by channel, and create blocks of transactions per channel.

The blocks of the transaction are delivered from the ordering node 284 to all peer nodes 281-283 on the channel. The transactions 294 within the block are validated to ensure any endorsement policy is fulfilled and to ensure that there have been no changes to ledger state for read set variables since the read set was generated by the transaction execution. Transactions in the block are tagged as being valid or invalid. Furthermore, in step 295 each peer node 281-283 appends the block to the channel's chain, and for each valid transaction the write sets are committed to current state database. An event is emitted, to notify the client application that the transaction (invocation) has been immutably appended to the chain, as well as to notify whether the transaction was validated or invalidated.

FIG. 3A illustrates an example of a permissioned blockchain network 300, which features a distributed, decentralized peer-to-peer architecture. In this example, a blockchain user 302 may initiate a transaction to the permissioned blockchain 304. In this example, the transaction can be a deploy, invoke, or query, and may be issued through a client-side application leveraging an SDK, directly through an API, etc. Networks may provide access to a regulator 306, such as an auditor. A blockchain network operator 308 manages member permissions, such as enrolling the regulator 306 as an “auditor” and the blockchain user 302 as a “client”. An auditor could be restricted only to querying the ledger whereas a client could be authorized to deploy, invoke, and query certain types of chaincode.

A blockchain developer 310 can write chaincode and client-side applications. The blockchain developer 310 can deploy chaincode directly to the network through an interface. To include credentials from a traditional data source 312 in chaincode, the developer 310 could use an out-of-band connection to access the data. In this example, the blockchain user 302 connects to the permissioned blockchain 304 through a peer node 314. Before proceeding with any transactions, the peer node 314 retrieves the user's enrollment and transaction certificates from a certificate authority 316, which manages user roles and permissions. In some cases, blockchain users must possess these digital certificates in order to transact on the permissioned blockchain 304. Meanwhile, a user attempting to utilize chaincode may be required to verify their credentials on the traditional data source 312. To confirm the user's authorization, chaincode can use an out-of-band connection to this data through a traditional processing platform 318.

FIG. 3B illustrates another example of a permissioned blockchain network 320, which features a distributed, decentralized peer-to-peer architecture. In this example, a blockchain user 322 may submit a transaction to the permissioned blockchain 324. In this example, the transaction can be a deploy, invoke, or query, and may be issued through a client-side application leveraging an SDK, directly through an API, etc. Networks may provide access to a regulator 326, such as an auditor. A blockchain network operator 328 manages member permissions, such as enrolling the regulator 326 as an “auditor” and the blockchain user 322 as a “client”. An auditor could be restricted only to querying the ledger whereas a client could be authorized to deploy, invoke, and query certain types of chaincode.

A blockchain developer 330 writes chaincode and client-side applications. The blockchain developer 330 can deploy chaincode directly to the network through an interface. To include credentials from a traditional data source 332 in chaincode, the developer 330 could use an out-of-band connection to access the data. In this example, the blockchain user 322 connects to the network through a peer node 334. Before proceeding with any transactions, the peer node 334 retrieves the user's enrollment and transaction certificates from the certificate authority 336. In some cases, blockchain users must possess these digital certificates in order to transact on the permissioned blockchain 324. Meanwhile, a user attempting to utilize chaincode may be required to verify their credentials on the traditional data source 332. To confirm the user's authorization, chaincode can use an out-of-band connection to this data through a traditional processing platform 338.

FIG. 4A illustrates a process 400 of adding a new active leaf node to a blockchain structure 410 (shown in FIG. 4A) which is stored on blockchain 401 (shown in FIG. 4B), according to example embodiments, and FIG. 4B illustrates a process 430 of invoking a new active leaf node 411B by a blockchain participant 431, according to example embodiments. In the example of FIG. 4A, the blockchain structure is a Merkle tree 410 which includes a first state 410A (also referred to as a current state), and a second state 410B (also referred to as an updated state) in which a new active leaf node 411B is added and the current active leaf node 411A is nullified, anonymously. In the example of FIG. 4A, three active leaf nodes 411, 412, and 413 are shown and correspond to three anonymous buyers of a supplier.

As described herein, a Merkle tree is a binary tree that may include a depth d where the tree is a complete binary tree of depth d. In this case, each of the leaf nodes store data which may be represented as a bit string of a fixed length. The value at each internal node in the tree may be a cryptographic hash (e.g., sha256, etc.) of a concatenation of values of a left and a right child node, in that order. In the examples herein, an empty Merkle tree may be initialized with all its leaf nodes set to some default value, for e.g. the all zeros bit string. Any new active leaf is added in place of the next available unused (i.e., having the default value) leaf node in the left to right order, and the values of the nodes on the path from the added leaf node up to and including the root node are updated. For example, for each buyer in the example of FIG. 1, a first active leaf is added and set to the standard cryptographic hash of an initial pre-image with a secret (made known only to the respective buyer) random bit string, a rating sum of zero (encoded as a bit string) and the number of ratings as zero (encoded as a bit string). The Merkle tree may be stored on a blockchain as part of the ledger corresponding to the smart contract. In an empty Merkle tree, all the nodes at the same depth have the same value. Thus, for memory efficiency, only the values of those nodes are explicitly stored which differ from the corresponding node in the empty Merkle tree.

As described in the examples herein, each active leaf may store or otherwise include anonymous behavior data of a participant (such as a buyer in the example of FIG. 1). In the examples herein, a smart contract maintains a Merkle tree for each supplier which contains an “active leaf” for each buyer of that supplier. The attributes that are maintained within a buyer's “active leaf” may include a standard cryptographic hash (sha256) value of the following pre-image: the concatenation of (i) a secret (known only to the buyer) random bit string, (ii) its current rating sum (encoded as a bit string), and (iii) its current number of ratings (encoded as a bit string). In the example of FIG. 4B, the current active leaf node 411A includes these respective attributes.

When a buyer wants to add a new rating of a supplier, the buyer may invoke a smart contract of the blockchain 401. In the example of FIG. 4B, an anonymous system 431 (such as one of the buyers 131-134 shown in FIG. 1) may request to update the buyer's active leaf with the supplier. In the example of FIG. 4B, the anonymous system 431 is associated with leaf node 411A and uploads a request 432 which includes a new active leaf node 411B. When the buyer (anonymous system 431) calls the smart contract to provide a new rating (request 432), the buyer provides the new active leaf 411B containing the standard cryptographic hash value of the following new pre-image: the concatenation of (i) a new secret random bit string (known only to the buyer, (ii) the updated rating sum, and (iii) the updated number of ratings. In addition, the buyer provides a nullifier of the existing active leaf 411A, which is a different, un-linkable cryptographic hash (e.g. sha256 with a non-standard initialization vector) of the pre-image of the existing active leaf 411A. Further, the Buyer provides a zero-knowledge proof (ZKP), as well as the rating it desires to submit.

According to various embodiments, the ZKP may show that the nullifier provided is indeed that of an existing active leaf in the Merkle tree, the current average rating given by the ratio of the current rating sum and the current number of ratings, is at least a given threshold (this check detects the anomalous behavior), and the new active leaf value is the standard cryptographic hash of the new pre-image given in 411B such that the updated rating sum is the rating sum of the existing active leaf in (ii) plus the provided rating, and updated number of ratings is the number of ratings of the existing active leaf in (iii) plus one.

The smart contract may verify that the newly provided nullifier is unused so as to ensure that the buyer must only nullify the current active leaf 411A and further verify the zero-knowledge proof provided above. If the check and verification pass, the list of ratings is updated with the provided rating, the new active leaf 411B is added to the Merkle-Tree and the provided nullifier is stored and marked as used. Note that in the above process, which current active leaf is nullified is not revealed as the verification is in zero-knowledge. The only guarantee is that some active leaf in the Merkle-Tree is nullified. Since multiple buyers exist for a supplier, each having an active leaf, the identity of the specific Buyer who is providing the rating is not revealed.

In the second state 410B, the existing active leaf 411A is nullified and stays in its location, and the new active leaf 411B associated with the same anonymous user is added in place of a first default/empty leaf in the left to right order. In this case, the default leaf signifies that this leaf node has some default value currently and has not been used to store any information yet. Therefore, in the second state 410B, the leaf L1 411A stays in place and is marked nullified. The new active leaf L1 411B is added in place of the default value.

The algorithm used for the zero-knowledge proof creation may be the ZKSnarks which is an open source implementation. Using the included gadgets, the predicate for the zero-knowledge proof may be implemented in libsnark to generate the proving and verification executables and the respective proving and verification keys. The buyer has the proving executable and key. As described above, the buyer computes the new active leaf and the nullifier of the current active leaf. To generate the proof, the buyer calls the smart contract to query the the values of the sibling nodes on the path from the current active leaf to the root.

The buyer may then privately generate (outside the blockchain/smart contract) the desired zero-knowledge proof using the libsnark proving executable and key with the following input values: the authentication path consisting of values on sibling nodes on the path from the current active leaf to the root, the components of the current active leaf's pre-image (e.g., the secret random bit string, the current rating sum, and the current number of ratings), the to-be provided new rating, and the new secret random string of the pre-image of the new active leaf. The output is the zero-knowledge proof which can be verified by a smart contract on the blockchain 401.

Likewise, when its time to verify the ZKP, the Smart Contract receives from the Buyer the new rating, the nullifier of the current active leaf, the new active leaf and the zero-knowledge proof. The smart contract may read the value of the Merkle tree root and run the libsnark verification executable along with the verification key with the following input values: the new rating, the nullifier of the current active leaf and the new active leaf, the Merkle tree root value, and the zero-knowledge proof.

The output of the above executable is a true/false value indicating whether the zero-knowledge proof is verified to prove that the nullifier provided is indeed that of an existing active leaf in the Merkle tree, the current average rating given by the ratio of the current rating sum and the current number of ratings, is at least a given threshold (this check detects the anomalous behavior), and the new active leaf value is the standard cryptographic hash of the new pre-image. The smart contract may be executed by an endorsing peer of the blockchain 401 which has the libsnark verification executable along with the verification key that which are accessible to the smart contract. In these examples, the smart contract does not know the current active leaf which is being nullified. Since the nullifier is un-linkable to the active leaf and the verification is in zero-knowledge, the smart contract does not gain any information about the current active leaf being nullified and thus the privacy of the buyer is preserved.

For example, the Smart Contract may be executed on the endorsing peer to verify the zero-knowledge proof provided by a buyer who calls the smart contract to anonymously add a rating for a supplier. The endorsing peer has the libsnark verification executable along with the verification key that are accessible to the smart contract. The zero-knowledge proof verification is done by the smart contract on behalf of the supplier who is guaranteed that anomalous (behavior) ratings by a buyer will be detected, at the same time preserving the privacy of the buyer.

If successful, the intended operations including the Merkle-Tree update, storing the rating and the nullifier, and the like, are performed by the smart contract, which involves updating a number of key-values in the ledger of the blockchain 401. The corresponding endorsed transaction which includes the read and write sets is created by the peer and transmitted as per the Blockchain protocol to be recorded in a block on the blockchain 401. The key-values in all the blockchain peers' ledgers are identically updated.

FIG. 4C illustrates a process 440 of managing a queue 450 which is implemented via a blockchain ledger and which can be used to prevent storage conflicts, according to example embodiments. In the Merkle tree described herein (or other shared or joint storage structure), a single invoke transaction uses a current active leaf and adds a new active leaf for a buyer. This can be done anonymously using the zero-knowledge proof. However, a problem may occur when multiple buyers (or other users) invoke the use/add-leaf transaction at the same time when adding a new leaf at the same index. This simultaneously invocation can lead to read/write conflicts (ref. Hyperledger Fabric v1), thus in each block at most one add leaf is possible. When the add-leaf operation is non-anonymous, conflicts can be resolved by collecting the new leaves and adding them in one aggregate transaction. However, this is not possible in an anonymous data storage because privacy is preserved. Although described with respect to a Merkle tree, a storage conflict can naturally arise in other zero-knowledge proof paradigms when using any kind of shared data structure modifiable anonymously by multiple parties.

To address this situation, a blockchain peer node 460 (smart contracts) may implement a queue 450 within a distributed blockchain ledger where new active leaf nodes (e.g., nodes 411B, 413B, 417C, and 415B) can be temporarily stored and subsequently added to the Merkle tree 410 in response to a flush operation. Once the ZK proof is verified, the nullifier is stored, and the rating is added, no additional information is needed for adding the new active leaf other than its value. The peer node 460 may store a collection of new active leaves in the queue 450 which can then be individually added together in a single transaction.

A smart contract application programming interface (API) framework may support special a BufferKeys operation which simulates a first-in-first-out (FIFO) queue 450 of string values. The queue 450 (or buffer) may be manipulated using various operations, including a DefineBufferKey operation which defines a particular key string to be a buffer key with an optional maximum size of buffer (e.g., DefineBufferKey(“Supplier1˜MT1˜LeafBuf”, 50)). The API framework may also support a BufPush operation which appends a value to an end of the queue 450. At the endorsement phase, the corresponding (BufferKey, value) write-set pair is generated. During block commitment on ledger, the values for a BufferKey are appended in the order of the transactions in the block. E.g. BufPush(“Supplier1˜MT1˜LeafBuf”, “1234”). The API framework may also support a BufFlush operation which returns an iterator to the values in the BufferKey, and the queue is flushed at commit phase. A transaction cannot have both a BufPush and BufFlush for the same key. Endorsement includes the BufferKey in a special flush set (e.g., BufFlush(“Supplier1˜MT1˜LeafBuf”)).

Accordingly, the queue 450 and the supporting push and flush operations can prevent a potential problem of conflict when multiple buyers attempt the add leaf operation on the Merkle tree simultaneously. This arises due to a common data structure, such as the Merkle tree, being modifiable anonymously by multiple parties (e.g., buyers). The operations such as BufferKeys along with the DefineBufferKey, BufPush and BufFlush operations in the Smart Contract API can be used to simulate a FIFO queue natively implemented in the blockchain ledger.

Using this enhancement, in the add-leaf operation the smart contract may push the new active leaf on a predefined BufferKey using the BufPush operation. Periodically, a designated party calls the BufFlush operation (e.g., chaincode of a designated peer, etc.) iterating through the to-be added active leaves and adds them to the Merkle tree 410. The example embodiments can therefore implement the smart contract method for storing anonymous data via Merkle trees based on zero-knowledge proofs for privacy preserving anomalous behavior detection on the blockchain, and the enhancement incorporating BufferKeys to the API and Blockchain ledger system for efficiently implementing the Merkle tree/zero-knowledge proof method to minimize conflicts. Note that the above issue of conflicts arises in blockchain networks where the transactions are executed, ordered and then committed—such as Hyperledger Fabric v1, and the enhancements described above are applicable to such blockchain networks.

FIG. 5A illustrates a method 510 of updating anonymous behavior on a blockchain structure, according to example embodiments. Referring to FIG. 5A, in 511, the method may include storing a tree structure via a blockchain storage. For example, the tree structure may include a Merkle tree, a binary tree, a non-binary tree, and the like. The anonymous behavior data may include anonymous behavior of a plurality of blockchain participants stored in a plurality of nodes in a hierarchical structure. In some embodiments, the tree structure may include a plurality of active leaf nodes storing anonymous behavior data for a plurality of blockchain participants, respectively, which do not reveal identities of the plurality of blockchain participants. The anonymous behavior may like an identity of the provider of the content. For example, the anonymous behavior may not identify a public key, a network address, a name, a device ID, an email address, a username, or the like, associated with the behavior.

In 512, the method may include receiving a request to add new anonymous behavior data to the tree structure. For example, the request may include a zero-knowledge proof generated by a blockchain participant, a nullifier of a previous active leaf of the blockchain participant, a new active leaf (anonymous data), and the like. For example, the zero-knowledge proof may include a random string that is known only to the blockchain participant which can be used to verify various attributes of the new active leaf node and its contents without revealing an identity of the blockchain participant. In some embodiments, the method may further include verifying a validity of the new anonymous behavior based on a root value of the tree structure, the zero-knowledge proof, and anonymous attributes of the new anonymous behavior.

In 513, the method may include identifying an active leaf on the tree structure which stores previously recorded anonymous behavior data of the blockchain participant associated with the request based on the zero-knowledge proof. In 514, the method may include generating a new active leaf for the blockchain participant based on the new anonymous behavior data and the previously recorded anonymous behavior. Here, the new active leaf may be used to replace the current active leaf. In some embodiments, the method may further include further include nullifying the identified active leaf on the tree structure with the new active leaf in response to receipt of the new anonymous behavior data. In 515, the method may include storing the new active leaf as a leaf node on the tree structure in the blockchain storage.

In some embodiments, the tree structure may include a Merkle tree which is stored via a key-value store of the blockchain storage, and the Merkle tree may include a respective active leaf node for each participant of the blockchain. In some embodiments, the anonymous behavior data may include anonymous reviews submitted by the blockchain participant. In some embodiments, the method may further include endorsing the new active leaf based on the zero-knowledge proof, prior to storing the new active leaf on the tree structure.

FIG. 5B illustrates a method 520 of managing a queue via a blockchain ledger, according to example embodiments. Here, the queue may be used to prevent conflicts from occurring when multiple participants attempt to add content to a blockchain storage structure at the same time. Referring to FIG. 5B, in 521, the method may include receiving a content request to add a content to a blockchain storage structure implemented on a blockchain database. For example, the content request may include a request to store a new node (e.g., an active leaf node, etc.) on a shared blockchain storage structure such as a binary tree, Merkle tree, etc. In some embodiments, the content request may include anonymous content that does not reveal an identity of a content creator. Here, the blockchain storage structure may store anonymous content of a plurality of content creators.

In 522, the method may include temporarily storing the content of the content request in a queue implemented via the blockchain database based on when the request is received. The queue may be implemented via a distributed ledger and controlled by a smart contract executing on peer nodes with the blockchain. In some embodiments, the queue may include a first-in first-out (FIFO) queue which is implemented via execute of the smart contract (chaincode) of the blockchain database. In 523, the method may include receiving a request to flush the queue which is invoked by chaincode. In response to the flush request, in 524, the method may include removing the content from the queue and adding the content to the blockchain storage structure. For example, the removing may include pushing the content from an end of the FIFO queue to a new node on a tree structure stored on the blockchain database.

In some embodiments, the receiving may include receiving a plurality of content requests to add a plurality of pieces of content to the blockchain storage structure, and the temporarily storing may include temporarily storing each piece of content as a respective entry in the queue. Here, the content may include new leaf nodes to be added as active leaf nodes to a Merkle tree. The nodes in the queue may be ordered based on when they are received so as to ensure correct chronological order. In some embodiments, the removing may include adding the content to an active leaf node on a Merkle tree storage structure implemented via the blockchain database. In some embodiments, the Merkle tree storage structure may be maintained within a key-value store (KVS) of the blockchain database.

FIG. 6A illustrates an example system 600 that includes a physical infrastructure 610 configured to perform various operations according to example embodiments. Referring to FIG. 6A, the physical infrastructure 610 includes a module 612 and a module 614. The module 614 includes a blockchain 620 and a smart contract 630 (which may reside on the blockchain 620), that may execute any of the operational steps 608 (in module 612) included in any of the example embodiments. The steps/operations 608 may include one or more of the embodiments described or depicted and may represent output or written information that is written or read from one or more smart contracts 630 and/or blockchains 620. The physical infrastructure 610, the module 612, and the module 614 may include one or more computers, servers, processors, memories, and/or wireless communication devices. Further, the module 612 and the module 614 may be a same module.

FIG. 6B illustrates another example system 640 configured to perform various operations according to example embodiments. Referring to FIG. 6B, the system 640 includes a module 612 and a module 614. The module 614 includes a blockchain 620 and a smart contract 630 (which may reside on the blockchain 620), that may execute any of the operational steps 608 (in module 612) included in any of the example embodiments. The steps/operations 608 may include one or more of the embodiments described or depicted and may represent output or written information that is written or read from one or more smart contracts 630 and/or blockchains 620. The physical infrastructure 610, the module 612, and the module 614 may include one or more computers, servers, processors, memories, and/or wireless communication devices. Further, the module 612 and the module 614 may be a same module.

FIG. 6C illustrates an example system configured to utilize a smart contract configuration among contracting parties and a mediating server configured to enforce the smart contract terms on the blockchain according to example embodiments. Referring to FIG. 6C, the configuration 650 may represent a communication session, an asset transfer session or a process or procedure that is driven by a smart contract 630 which explicitly identifies one or more user devices 652 and/or 656. The execution, operations and results of the smart contract execution may be managed by a server 654. Content of the smart contract 630 may require digital signatures by one or more of the entities 652 and 656 which are parties to the smart contract transaction. The results of the smart contract execution may be written to a blockchain 620 as a blockchain transaction. The smart contract 630 resides on the blockchain 620 which may reside on one or more computers, servers, processors, memories, and/or wireless communication devices.

FIG. 6D illustrates a system 660 including a blockchain, according to example embodiments. Referring to the example of FIG. 6D, an application programming interface (API) gateway 662 provides a common interface for accessing blockchain logic (e.g., smart contract 630 or other chaincode) and data (e.g., distributed ledger, etc.). In this example, the API gateway 662 is a common interface for performing transactions (invoke, queries, etc.) on the blockchain by connecting one or more entities 652 and 656 to a blockchain peer (i.e., server 654). Here, the server 654 is a blockchain network peer component that holds a copy of the world state and a distributed ledger allowing clients 652 and 656 to query data on the world state as well as submit transactions into the blockchain network where, depending on the smart contract 630 and endorsement policy, endorsing peers will run the smart contracts 630.

The above embodiments may be implemented in hardware, in a computer program executed by a processor, in firmware, or in a combination of the above. A computer program may be embodied on a computer readable medium, such as a storage medium. For example, a computer program may reside in random access memory (“RAM”), flash memory, read-only memory (“ROM”), erasable programmable read-only memory (“EPROM”), electrically erasable programmable read-only memory (“EEPROM”), registers, hard disk, a removable disk, a compact disk read-only memory (“CD-ROM”), or any other form of storage medium known in the art.

An exemplary storage medium may be coupled to the processor such that the processor may read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an application specific integrated circuit (“ASIC”). In the alternative, the processor and the storage medium may reside as discrete components.

FIG. 7A illustrates a process 700 of a new block being added to a distributed ledger 720, according to example embodiments, and FIG. 7B illustrates contents of a new data block structure 730 for blockchain, according to example embodiments. Referring to FIG. 7A, clients (not shown) may submit transactions to blockchain nodes 711, 712, and/or 713. Clients may be instructions received from any source to enact activity on the blockchain 720. As an example, clients may be applications that act on behalf of a requester, such as a device, person or entity to propose transactions for the blockchain. The plurality of blockchain peers (e.g., blockchain nodes 711, 712, and 713) may maintain a state of the blockchain network and a copy of the distributed ledger 720. Different types of blockchain nodes/peers may be present in the blockchain network including endorsing peers which simulate and endorse transactions proposed by clients and committing peers which verify endorsements, validate transactions, and commit transactions to the distributed ledger 720. In this example, the blockchain nodes 711, 712, and 713 may perform the role of endorser node, committer node, or both.

The distributed ledger 720 includes a blockchain which stores immutable, sequenced records in blocks, and a state database 724 (current world state) maintaining a current state of the blockchain 722. One distributed ledger 720 may exist per channel and each peer maintains its own copy of the distributed ledger 720 for each channel of which they are a member. The blockchain 722 is a transaction log, structured as hash-linked blocks where each block contains a sequence of N transactions. Blocks may include various components such as shown in FIG. 7B. The linking of the blocks (shown by arrows in FIG. 7A) may be generated by adding a hash of a prior block's header within a block header of a current block. In this way, all transactions on the blockchain 722 are sequenced and cryptographically linked together preventing tampering with blockchain data without breaking the hash links. Furthermore, because of the links, the latest block in the blockchain 722 represents every transaction that has come before it. The blockchain 722 may be stored on a peer file system (local or attached storage), which supports an append-only blockchain workload.

The current state of the blockchain 722 and the distributed ledger 722 may be stored in the state database 724. Here, the current state data represents the latest values for all keys ever included in the chain transaction log of the blockchain 722. Chaincode invocations execute transactions against the current state in the state database 724. To make these chaincode interactions extremely efficient, the latest values of all keys are stored in the state database 724. The state database 724 may include an indexed view into the transaction log of the blockchain 722, it can therefore be regenerated from the chain at any time. The state database 724 may automatically get recovered (or generated if needed) upon peer startup, before transactions are accepted.

Endorsing nodes receive transactions from clients and endorse the transaction based on simulated results. Endorsing nodes hold smart contracts which simulate the transaction proposals. When an endorsing node endorses a transaction, the endorsing nodes creates a transaction endorsement which is a signed response from the endorsing node to the client application indicating the endorsement of the simulated transaction. The method of endorsing a transaction depends on an endorsement policy which may be specified within chaincode. An example of an endorsement policy is “the majority of endorsing peers must endorse the transaction”. Different channels may have different endorsement policies. Endorsed transactions are forward by the client application to ordering service 710.

The ordering service 710 accepts endorsed transactions, orders them into a block, and delivers the blocks to the committing peers. For example, the ordering service 710 may initiate a new block when a threshold of transactions has been reached, a timer times out, or another condition. In the example of FIG. 7A, blockchain node 712 is a committing peer that has received a new data new data block 730 for storage on blockchain 720. The first block in the blockchain may be referred to as a genesis block which includes information about the blockchain, its members, the data stored therein, etc.

The ordering service 710 may be made up of a cluster of orderers. The ordering service 710 does not process transactions, smart contracts, or maintain the shared ledger. Rather, the ordering service 710 may accept the endorsed transactions and specifies the order in which those transactions are committed to the distributed ledger 720. The architecture of the blockchain network may be designed such that the specific implementation of ‘ordering’ (e.g., Solo, Kafka, BFT, etc.) becomes a pluggable component.

Transactions are written to the distributed ledger 720 in a consistent order. The order of transactions is established to ensure that the updates to the state database 724 are valid when they are committed to the network. Unlike a cryptocurrency blockchain system (e.g., Bitcoin, etc.) where ordering occurs through the solving of a cryptographic puzzle, or mining, in this example the parties of the distributed ledger 720 may choose the ordering mechanism that best suits that network.

When the ordering service 710 initializes a new data block 730, the new data block 730 may be broadcast to committing peers (e.g., blockchain nodes 711, 712, and 713). In response, each committing peer validates the transaction within the new data block 730 by checking to make sure that the read set and the write set still match the current world state in the state database 724. Specifically, the committing peer can determine whether the read data that existed when the endorsers simulated the transaction is identical to the current world state in the state database 724. When the committing peer validates the transaction, the transaction is written to the blockchain 722 on the distributed ledger 720, and the state database 724 is updated with the write data from the read-write set. If a transaction fails, that is, if the committing peer finds that the read-write set does not match the current world state in the state database 724, the transaction ordered into a block will still be included in that block, but it will be marked as invalid, and the state database 724 will not be updated.

Referring to FIG. 7B, a new data block 730 (also referred to as a data block) that is stored on the blockchain 722 of the distributed ledger 720 may include multiple data segments such as a block header 740, block data 750, and block metadata 760. It should be appreciated that the various depicted blocks and their contents, such as new data block 730 and its contents. shown in FIG. 7B are merely examples and are not meant to limit the scope of the example embodiments. The new data block 730 may store transactional information of N transaction(s) (e.g., 1, 10, 100, 500, 1000, 2000, 3000, etc.) within the block data 750. The new data block 730 may also include a link to a previous block (e.g., on the blockchain 722 in FIG. 7A) within the block header 740. In particular, the block header 740 may include a hash of a previous block's header. The block header 740 may also include a unique block number, a hash of the block data 750 of the new data block 730, and the like. The block number of the new data block 730 may be unique and assigned in various orders, such as an incremental/sequential order starting from zero.

The block data 750 may store transactional information of each transaction that is recorded within the new data block 730. For example, the transaction data may include one or more of a type of the transaction, a version, a timestamp, a channel ID of the distributed ledger 720, a transaction ID, an epoch, a payload visibility, a chaincode path (deploy tx), a chaincode name, a chaincode version, input (chaincode and functions), a client (creator) identify such as a public key and certificate, a signature of the client, identities of endorsers, endorser signatures, a proposal hash, chaincode events, response status, namespace, a read set (list of key and version read by the transaction, etc.), a write set (list of key and value, etc.), a start key, an end key, a list of keys, a Merkel tree query summary, and the like. The transaction data may be stored for each of the N transactions.

In some embodiments, the block data 750 may also store anonymous data 752 such as anonymous activity, behavior, participation, etc. of a user within a larger group of users. In doing so, the block data 750 includes additional information which is added to the hash-linked chain of blocks in the blockchain 722. For example, the additional information may include a Merkle tree (or other structure) including anonymous data 752 of various sources. The anonymous data 752 may include a secret known only by the submitted of the data, an accumulation of behavior, a number of entries on the Merkle tree, and the like. Accordingly, the anonymous data 752 can be stored in an immutable ledger via a key-value store which is included in the distributed ledger 720. Some of the benefits of storing such anonymous data 752 are reflected in the various embodiments disclosed and depicted herein. Although in FIG. 7B the anonymous data 752 is depicted in the block data 750, it could also be located in the block header 740 or the block metadata 760, or other areas of the distributed ledger besides the blockchain such as a key-value store, a world-state database, and the like.

The block metadata 760 may store multiple fields of metadata (e.g., as a byte array, etc.). Metadata fields may include signature on block creation, a reference to a last configuration block, a transaction filter identifying valid and invalid transactions within the block, last offset persisted of an ordering service that ordered the block, and the like. The signature, the last configuration block, and the orderer metadata may be added by the ordering service 710. Meanwhile, a committer of the block (such as blockchain node 712) may add validity/invalidity information based on an endorsement policy, verification of read/write sets, and the like. The transaction filter may include a byte array of a size equal to the number of transactions in the block data 750 and a validation code identifying whether a transaction was valid/invalid.

FIG. 7C illustrates an embodiment of a blockchain 770 for digital content in accordance with the embodiments described herein. The digital content may include one or more files and associated information. The files may include media, images, video, audio, text, links, graphics, animations, web pages, documents, or other forms of digital content. The immutable, append-only aspects of the blockchain serve as a safeguard to protect the integrity, validity, and authenticity of the digital content, making it suitable use in legal proceedings where admissibility rules apply or other settings where evidence is taken in to consideration or where the presentation and use of digital information is otherwise of interest. In this case, the digital content may be referred to as digital evidence.

The blockchain may be formed in various ways. In one embodiment, the digital content may be included in and accessed from the blockchain itself. For example, each block of the blockchain may store a hash value of reference information (e.g., header, value, etc.) along the associated digital content. The hash value and associated digital content may then be encrypted together. Thus, the digital content of each block may be accessed by decrypting each block in the blockchain, and the hash value of each block may be used as a basis to reference a previous block. This may be illustrated as follows:

Block 1 Block 2 . . . Block N Hash Value 1 Hash Value 2 Hash Value N Digital Content 1 Digital Content 2 Digital Content N

In one embodiment, the digital content may be not included in the blockchain. For example, the blockchain may store the encrypted hashes of the content of each block without any of the digital content. The digital content may be stored in another storage area or memory address in association with the hash value of the original file. The other storage area may be the same storage device used to store the blockchain or may be a different storage area or even a separate relational database. The digital content of each block may be referenced or accessed by obtaining or querying the hash value of a block of interest and then looking up that has value in the storage area, which is stored in correspondence with the actual digital content. This operation may be performed, for example, a database gatekeeper. This may be illustrated as follows:

Blockchain Storage Area Block 1 Hash Value Block 1 Hash Value . . . Content . . . . . . Block N Hash Value Block N Hash Value . . . Content

In the example embodiment of FIG. 7C, the blockchain 770 includes a number of blocks 778 ₁, 778 ₂, . . . 778 _(N) cryptographically linked in an ordered sequence, where N>1. The encryption used to link the blocks 778 ₁, 778 ₂, . . . 778 _(N) may be any of a number of keyed or un-keyed Hash functions. In one embodiment, the blocks 778 ₁, 778 ₂, . . . 778 _(N) are subject to a hash function which produces n-bit alphanumeric outputs (where n is 256 or another number) from inputs that are based on information in the blocks. Examples of such a hash function include, but are not limited to, a SHA-type (SHA stands for Secured Hash Algorithm) algorithm, Merkle-Damgard algorithm, HAIFA algorithm, Merkle-tree algorithm, nonce-based algorithm, and a non-collision-resistant PRF algorithm. In another embodiment, the blocks 778 ₁, 778 ₂, . . . , 778 _(N) may be cryptographically linked by a function that is different from a hash function. For purposes of illustration, the following description is made with reference to a hash function, e.g., SHA-2.

Each of the blocks 778 ₁, 778 ₂, . . . , 778 _(N) in the blockchain includes a header, a version of the file, and a value. The header and the value are different for each block as a result of hashing in the blockchain. In one embodiment, the value may be included in the header. As described in greater detail below, the version of the file may be the original file or a different version of the original file.

The first block 778 ₁ in the blockchain is referred to as the genesis block and includes the header 772 ₁, original file 774 ₁, and an initial value 776 ₁. The hashing scheme used for the genesis block, and indeed in all subsequent blocks, may vary. For example, all the information in the first block 778 ₁ may be hashed together and at one time, or each or a portion of the information in the first block 778 ₁ may be separately hashed and then a hash of the separately hashed portions may be performed.

The header 772 ₁ may include one or more initial parameters, which, for example, may include a version number, timestamp, nonce, root information, difficulty level, consensus protocol, duration, media format, source, descriptive keywords, and/or other information associated with original file 774 ₁ and/or the blockchain. The header 772 ₁ may be generated automatically (e.g., by blockchain network managing software) or manually by a blockchain participant. Unlike the header in other blocks 778 ₂ to 778 _(N) in the blockchain, the header 772 ₁ in the genesis block does not reference a previous block, simply because there is no previous block.

The original file 774 ₁ in the genesis block may be, for example, data as captured by a device with or without processing prior to its inclusion in the blockchain. The original file 774 ₁ is received through the interface of the system from the device, media source, or node. The original file 774 ₁ is associated with metadata, which, for example, may be generated by a user, the device, and/or the system processor, either manually or automatically. The metadata may be included in the first block 778 ₁ in association with the original file 774 ₁.

The value 776 ₁ in the genesis block is an initial value generated based on one or more unique attributes of the original file 774 ₁. In one embodiment, the one or more unique attributes may include the hash value for the original file 774 ₁, metadata for the original file 774 ₁, and other information associated with the file. In one implementation, the initial value 776 ₁ may be based on the following unique attributes:

-   -   1) SHA-2 computed hash value for the original file     -   2) originating device ID     -   3) starting timestamp for the original file     -   4) initial storage location of the original file     -   5) blockchain network member ID for software to currently         control the original file and associated metadata

The other blocks 778 ₂ to 778 _(N) in the blockchain also have headers, files, and values. However, unlike the first block 772 ₁, each of the headers 772 ₂ to 772 _(N) in the other blocks includes the hash value of an immediately preceding block. The hash value of the immediately preceding block may be just the hash of the header of the previous block or may be the hash value of the entire previous block. By including the hash value of a preceding block in each of the remaining blocks, a trace can be performed from the Nth block back to the genesis block (and the associated original file) on a block-by-block basis, as indicated by arrows 780, to establish an auditable and immutable chain-of-custody.

Each of the header 772 ₂ to 772 _(N) in the other blocks may also include other information, e.g., version number, timestamp, nonce, root information, difficulty level, consensus protocol, and/or other parameters or information associated with the corresponding files and/or the blockchain in general.

The files 774 ₂ to 774 _(N) in the other blocks may be equal to the original file or may be a modified version of the original file in the genesis block depending, for example, on the type of processing performed. The type of processing performed may vary from block to block. The processing may involve, for example, any modification of a file in a preceding block, such as redacting information or otherwise changing the content of, taking information away from, or adding or appending information to the files.

Additionally, or alternatively, the processing may involve merely copying the file from a preceding block, changing a storage location of the file, analyzing the file from one or more preceding blocks, moving the file from one storage or memory location to another, or performing action relative to the file of the blockchain and/or its associated metadata. Processing which involves analyzing a file may include, for example, appending, including, or otherwise associating various analytics, statistics, or other information associated with the file.

The values in each of the other blocks 776 ₂ to 776 _(N) in the other blocks are unique values and are all different as a result of the processing performed. For example, the value in any one block corresponds to an updated version of the value in the previous block. The update is reflected in the hash of the block to which the value is assigned. The values of the blocks therefore provide an indication of what processing was performed in the blocks and also permit a tracing through the blockchain back to the original file. This tracking confirms the chain-of-custody of the file throughout the entire blockchain.

For example, consider the case where portions of the file in a previous block are redacted, blocked out, or pixelated in order to protect the identity of a person shown in the file. In this case, the block including the redacted file will include metadata associated with the redacted file, e.g., how the redaction was performed, who performed the redaction, timestamps where the redaction(s) occurred, etc. The metadata may be hashed to form the value. Because the metadata for the block is different from the information that was hashed to form the value in the previous block, the values are different from one another and may be recovered when decrypted.

In one embodiment, the value of a previous block may be updated (e.g., a new hash value computed) to form the value of a current block when any one or more of the following occurs. The new hash value may be computed by hashing all or a portion of the information noted below, in this example embodiment.

-   -   a) new SHA-2 computed hash value if the file has been processed         in any way (e.g., if the file was redacted, copied, altered,         accessed, or some other action was taken)     -   b) new storage location for the file     -   c) new metadata identified associated with the file     -   d) transfer of access or control of the file from one blockchain         participant to another blockchain participant

FIG. 7D illustrates an embodiment of a block which may represent the structure of the blocks in the blockchain 790 in accordance with one embodiment. The block, Block_(i), includes a header 772 _(i), a file 774 _(i), and a value 776 _(i).

The header 772 _(i) includes a hash value of a previous block Block_(i-1) and additional reference information, which, for example, may be any of the types of information (e.g., header information including references, characteristics, parameters, etc.) discussed herein. All blocks reference the hash of a previous block except, of course, the genesis block. The hash value of the previous block may be just a hash of the header in the previous block or a hash of all or a portion of the information in the previous block, including the file and metadata.

The file 774 _(i) includes a plurality of data, such as Data 1, Data 2, . . . , Data N in sequence. The data are tagged with metadata Metadata 1, Metadata 2, . . . , Metadata N which describe the content and/or characteristics associated with the data. For example, the metadata for each data may include information to indicate a timestamp for the data, process the data, keywords indicating the persons or other content depicted in the data, and/or other features that may be helpful to establish the validity and content of the file as a whole, and particularly its use a digital evidence, for example, as described in connection with an embodiment discussed below. In addition to the metadata, each data may be tagged with reference REF₁, REF₂, . . . , REF_(N) to a previous data to prevent tampering, gaps in the file, and sequential reference through the file.

Once the metadata is assigned to the data (e.g., through a smart contract), the metadata cannot be altered without the hash changing, which can easily be identified for invalidation. The metadata, thus, creates a data log of information that may be accessed for use by participants in the blockchain.

The value 776 _(i) is a hash value or other value computed based on any of the types of information previously discussed. For example, for any given block Block_(i), the value for that block may be updated to reflect the processing that was performed for that block, e.g., new hash value, new storage location, new metadata for the associated file, transfer of control or access, identifier, or other action or information to be added. Although the value in each block is shown to be separate from the metadata for the data of the file and header, the value may be based, in part or whole, on this metadata in another embodiment.

Once the blockchain 770 is formed, at any point in time, the immutable chain-of-custody for the file may be obtained by querying the blockchain for the transaction history of the values across the blocks. This query, or tracking procedure, may begin with decrypting the value of the block that is most currently included (e.g., the last (N^(th)) block), and then continuing to decrypt the value of the other blocks until the genesis block is reached and the original file is recovered. The decryption may involve decrypting the headers and files and associated metadata at each block, as well.

Decryption is performed based on the type of encryption that took place in each block. This may involve the use of private keys, public keys, or a public key-private key pair. For example, when asymmetric encryption is used, blockchain participants or a processor in the network may generate a public key and private key pair using a predetermined algorithm. The public key and private key are associated with each other through some mathematical relationship. The public key may be distributed publicly to serve as an address to receive messages from other users, e.g., an IP address or home address. The private key is kept secret and used to digitally sign messages sent to other blockchain participants. The signature is included in the message so that the recipient can verify using the public key of the sender. This way, the recipient can be sure that only the sender could have sent this message.

Generating a key pair may be analogous to creating an account on the blockchain, but without having to actually register anywhere. Also, every transaction that is executed on the blockchain is digitally signed by the sender using their private key. This signature ensures that only the owner of the account can track and process (if within the scope of permission determined by a smart contract) the file of the blockchain.

FIG. 8 illustrates an example system 800 that supports one or more of the example embodiments described and/or depicted herein. The system 800 comprises a computer system/server 802, which is operational with numerous other general purpose or special purpose computing system environments or configurations. Examples of well-known computing systems, environments, and/or configurations that may be suitable for use with computer system/server 802 include, but are not limited to, personal computer systems, server computer systems, thin clients, thick clients, hand-held or laptop devices, multiprocessor systems, microprocessor-based systems, set top boxes, programmable consumer electronics, network PCs, minicomputer systems, mainframe computer systems, and distributed cloud computing environments that include any of the above systems or devices, and the like.

Computer system/server 802 may be described in the general context of computer system-executable instructions, such as program modules, being executed by a computer system. Generally, program modules may include routines, programs, objects, components, logic, data structures, and so on that perform particular tasks or implement particular abstract data types. Computer system/server 802 may be practiced in distributed cloud computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed cloud computing environment, program modules may be located in both local and remote computer system storage media including memory storage devices.

As shown in FIG. 8, computer system/server 802 in cloud computing node 800 is shown in the form of a general-purpose computing device. The components of computer system/server 802 may include, but are not limited to, one or more processors or processing units 804, a system memory 806, and a bus that couples various system components including system memory 806 to processor 804.

The bus represents one or more of any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures. By way of example, and not limitation, such architectures include Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnects (PCI) bus.

Computer system/server 802 typically includes a variety of computer system readable media. Such media may be any available media that is accessible by computer system/server 802, and it includes both volatile and non-volatile media, removable and non-removable media. System memory 806, in one embodiment, implements the flow diagrams of the other figures. The system memory 806 can include computer system readable media in the form of volatile memory, such as random-access memory (RAM) 810 and/or cache memory 812. Computer system/server 802 may further include other removable/non-removable, volatile/non-volatile computer system storage media. By way of example only, storage system 814 can be provided for reading from and writing to a non-removable, non-volatile magnetic media (not shown and typically called a “hard drive”). Although not shown, a magnetic disk drive for reading from and writing to a removable, non-volatile magnetic disk (e.g., a “floppy disk”), and an optical disk drive for reading from or writing to a removable, non-volatile optical disk such as a CD-ROM, DVD-ROM or other optical media can be provided. In such instances, each can be connected to the bus by one or more data media interfaces. As will be further depicted and described below, memory 806 may include at least one program product having a set (e.g., at least one) of program modules that are configured to carry out the functions of various embodiments of the application.

Program/utility 816, having a set (at least one) of program modules 818, may be stored in memory 806 by way of example, and not limitation, as well as an operating system, one or more application programs, other program modules, and program data. Each of the operating system, one or more application programs, other program modules, and program data or some combination thereof, may include an implementation of a networking environment. Program modules 818 generally carry out the functions and/or methodologies of various embodiments of the application as described herein.

As will be appreciated by one skilled in the art, aspects of the present application may be embodied as a system, method, or computer program product. Accordingly, aspects of the present application may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present application may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

Computer system/server 802 may also communicate with one or more external devices 820 such as a keyboard, a pointing device, a display 822, etc.; one or more devices that enable a user to interact with computer system/server 802; and/or any devices (e.g., network card, modem, etc.) that enable computer system/server 802 to communicate with one or more other computing devices. Such communication can occur via I/O interfaces 824. Still yet, computer system/server 802 can communicate with one or more networks such as a local area network (LAN), a general wide area network (WAN), and/or a public network (e.g., the Internet) via network adapter 826. As depicted, network adapter 826 communicates with the other components of computer system/server 802 via a bus. It should be understood that although not shown, other hardware and/or software components could be used in conjunction with computer system/server 802. Examples, include, but are not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data archival storage systems, etc.

Although an exemplary embodiment of at least one of a system, method, and non-transitory computer readable medium has been illustrated in the accompanied drawings and described in the foregoing detailed description, it will be understood that the application is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substitutions as set forth and defined by the following claims. For example, the capabilities of the system of the various figures can be performed by one or more of the modules or components described herein or in a distributed architecture and may include a transmitter, receiver or pair of both. For example, all or part of the functionality performed by the individual modules, may be performed by one or more of these modules. Further, the functionality described herein may be performed at various times and in relation to various events, internal or external to the modules or components. Also, the information sent between various modules can be sent between the modules via at least one of: a data network, the Internet, a voice network, an Internet Protocol network, a wireless device, a wired device and/or via plurality of protocols. Also, the messages sent or received by any of the modules may be sent or received directly and/or via one or more of the other modules.

One skilled in the art will appreciate that a “system” could be embodied as a personal computer, a server, a console, a personal digital assistant (PDA), a cell phone, a tablet computing device, a smartphone or any other suitable computing device, or combination of devices. Presenting the above-described functions as being performed by a “system” is not intended to limit the scope of the present application in any way but is intended to provide one example of many embodiments. Indeed, methods, systems and apparatuses disclosed herein may be implemented in localized and distributed forms consistent with computing technology.

It should be noted that some of the system features described in this specification have been presented as modules, in order to more particularly emphasize their implementation independence. For example, a module may be implemented as a hardware circuit comprising custom very large-scale integration (VLSI) circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices, graphics processing units, or the like.

A module may also be at least partially implemented in software for execution by various types of processors. An identified unit of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions that may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module need not be physically located together but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the module and achieve the stated purpose for the module. Further, modules may be stored on a computer-readable medium, which may be, for instance, a hard disk drive, flash device, random access memory (RAM), tape, or any other such medium used to store data.

Indeed, a module of executable code could be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network.

It will be readily understood that the components of the application, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the detailed description of the embodiments is not intended to limit the scope of the application as claimed but is merely representative of selected embodiments of the application.

One having ordinary skill in the art will readily understand that the above may be practiced with steps in a different order, and/or with hardware elements in configurations that are different than those which are disclosed. Therefore, although the application has been described based upon these preferred embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent.

While preferred embodiments of the present application have been described, it is to be understood that the embodiments described are illustrative only and the scope of the application is to be defined solely by the appended claims when considered with a full range of equivalents and modifications (e.g., protocols, hardware devices, software platforms etc.) thereto. 

What is claimed is:
 1. A computing system comprising: a network interface configured to receive a content request to add content to a blockchain storage structure implemented on a blockchain database; and a processor configured to temporarily store the content of the content request in a queue implemented via the blockchain database based on when the request is received, receive a request to flush the queue which is invoked by chaincode, and in response to the flush request, remove the content from the queue and add the content to the blockchain storage structure.
 2. The computing system of claim 1, wherein the queue comprises a first-in first-out (FIFO) queue which is implemented via chaincode of the blockchain database.
 3. The computing system of claim 2, wherein the processor is configured to push the content out from an end of the FIFO queue to a new node on a tree structure stored on the blockchain database.
 4. The computing system of claim 1, wherein the network interface is configured to receive a plurality of content requests to add a plurality of pieces of content to the blockchain storage structure, and the processor is configured to temporarily store each piece of content as a respective entry in the queue.
 5. The computing system of claim 1, wherein the processor is configured to add the content within an active leaf node on a Merkle tree storage structure implemented via the blockchain database.
 6. The computing system of claim 5, wherein the processor maintains the Merkle tree storage structure within a key-value store (KVS) of the blockchain database.
 7. The computing system of claim 1, wherein the content request comprises anonymous content that does not reveal an identity of a content creator.
 8. The computing system of claim 1, wherein the blockchain storage structure stores anonymous content of a plurality of content creators.
 9. A method comprising: receiving a content request to add a content to a blockchain storage structure implemented on a blockchain database; temporarily storing the content of the content request in a queue implemented via the blockchain database based on when the request is received; receiving a request to flush the queue which is invoked by chaincode; and in response to the flush request, removing the content from the queue and adding the content to the blockchain storage structure.
 10. The method of claim 9, wherein the queue comprises a first-in first-out (FIFO) queue which is implemented via chaincode of the blockchain database.
 11. The method of claim 10, wherein the removing comprises pushing the content from an end of the FIFO queue to a new node on a tree structure stored on the blockchain database.
 12. The method of claim 9, wherein the receiving comprises receiving a plurality of content requests to add a plurality of pieces of content to the blockchain storage structure, and the temporarily storing comprises temporarily storing each piece of content as a respective entry in the queue.
 13. The method of claim 9, wherein the removing comprises adding the content to an active leaf node on a Merkle tree storage structure implemented via the blockchain database.
 14. The method of claim 13, wherein the Merkle tree storage structure is maintained within a key-value store (KVS) of the blockchain database.
 15. The method of claim 9, wherein the content request comprises anonymous content that does not reveal an identity of a content creator.
 16. The method of claim 9, wherein the blockchain storage structure stores anonymous content of a plurality of content creators.
 17. A non-transitory computer readable medium comprising instructions, that when read by a processor, cause the processor to perform a method comprising: receiving a content request to add a content to a blockchain storage structure implemented on a blockchain database; temporarily storing the content of the content request in a queue implemented via the blockchain database based on when the request is received; receiving a request to flush the queue which is invoked by chaincode; and in response to the flush request, removing the content from the queue and adding the content to the blockchain storage structure.
 18. The non-transitory computer-readable medium of claim 17, wherein the queue comprises a first-in first-out (FIFO) queue which is implemented via chaincode of the blockchain database.
 19. The non-transitory computer-readable medium of claim 17, wherein the removing comprises pushing the content from an end of the FIFO queue to a new node on a tree structure stored on the blockchain database.
 20. The non-transitory computer-readable medium of claim 17, wherein the removing comprises adding the content to an active leaf node on a Merkle tree storage structure implemented via the blockchain database. 